don't compute the bounding sphere.

seems to improve performance and i don't quite know what it's used for
anyway.

js/pixl/public/thrixl.html

				}
			}
			chunkGeometry.computeBoundingSphere();
			var material = new THREE.MeshBasicMaterial({color: 0x00ff00});
			return new THREE.Mesh(chunkGeometry, material);
		}